Intracardiac capsule and an implantation accessory for use with the femoral artery

ABSTRACT

An assembly including an autonomous capsule having an anchoring member adapted to penetrate tissue of the heart and an accessory for implantation of the capsule. The accessory includes a steerable catheter with an inner lumen, having at its distal end a tubular protection tip defining a volume for housing the capsule. The accessory also includes a disconnectable attachment mechanism for supporting and guiding the capsule to an implantation site and a sub-catheter housed within the lumen of the steerable catheter, moveable in translation and in rotation relative to the steerable catheter. The sub-catheter and the capsule are movable between a retracted position and a position wherein the capsule is deployed out of the protection tip. The sub-catheter and the capsule are provided with a first fastening mechanism for fastening the two in translation and in mutual rotation, which is disconnectable under a rotation applied to the sub-catheter.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 15/894,541 filed Feb. 12, 2018 which is acontinuation application of U.S. patent application Ser. No. 14/312,381filed Jun. 23, 2014, which claims the benefit of and priority to FrenchPatent Application No. 1356020, filed Jun. 24, 2013, both of which arehereby incorporated by reference herein in their entireties.

BACKGROUND

The invention relates to “active implantable medical devices” as definedby Directive 90/385/EEC of 20 Jun. 1990 of the Council of the EuropeanCommunities, specifically implants to continuously monitor heart rhythmand deliver, if necessary, electrical pulses to the heart forstimulation, resynchronization and/or defibrillation in case of rhythmdisorder detected by the device.

The invention relates, in general, to the in situ implantation of suchdevices provided at the distal end with an anchoring device adapted topenetrate the tissue of a body wall at the chosen implantation site.

A typical example of such an anchoring member is a projecting helicalscrew axially extending from the medical device body and adapted topenetrate the heart tissue by a screwing motion at the implantationsite. However, this anchoring arrangement is not limitative of theinvention, which also applies to other types of anchoring members, forexample by implementation of needles, hooks, barbs, etc., penetratingtissue for permanently fixing the medical device.

According to a first aspect, the invention more particularly relates tothose devices that are in the form of an autonomous capsule implanted ina heart chamber (ventricle, atrium or even arterial left heart chamber).The device will be hereinafter referred to as “autonomous capsule” or“leadless capsule” (the autonomous character of the capsule, albeit notintrinsically, being a necessary feature of the invention). Theseautonomous capsules are devoid of any physical connection to a mainimplanted device (such as the housing of a stimulation pulse generator)or not implanted device (external device such as a programmer ormonitoring device for remote monitoring of the patient). Accordingly,the capsules are referred to as “leadless capsules”, to distinguish themfrom electrodes or sensors located at the distal end of a conventionallead, which is traversed throughout its length with one or moreconductors galvanically connecting the electrode or sensor to aconnected generator at an opposite, proximal, end to the lead.

It will be seen that, according to a second aspect, the invention can begeneralized to the “delivery”. That is to say the implantation in theselected site of implantation of other types of medical devices. In oneexample, such devices may be stimulation leads in the form of a tubularbody having at its distal end an anchoring mechanism for anchoring to aheart wall and an active portion provided with detection/stimulationelectrodes, and at its proximal end, mechanical and electricalconnection to the housing of a generator that is remotely implanted fromthe site of application of the pulses. The invention can be applied tostill other types of implantable devices, for example to capsulesintended for release in situ of an active pharmacological agent.

When the leadless capsules are endocardial capsules (capsules attachedto the inner wall of an atrial or ventricular chamber, as opposed toepicardial capsules fixed to the external wall of the heart), theimplantation constraints are increased because of the surgery approach.The approach for endocardial implantation involves going through theperipheral venous system and directs, under image intensifier, thecapsule to the selected implantation site. This in a both precise andperfectly secure method. It is only once the site is reached and thecapsule is firmly attached in the heart wall that the operator mayproceed to the “release” of the capsule, or more particularly, itsdisconnection from the implantation accessory.

U.S. 2012/0095539 A1 discloses an implantation accessory for anendocardial electrostimulation leadless capsule. This accessory includesa steerable catheter carrying the capsule. The steerable catheter housesin its inner lumen at its end a wire which is distally connected to thecapsule and which is operable in translation and rotation from theproximal end by a handle provided for the practitioner. In a firstembodiment, the capsule is mounted to the catheter tip by a system ofmale/female nesting and the wire end is screwed to the back of thecapsule. The retention wire keeps the two elements of the couplingsystem fitted into each other by a slight tension on the wire, thelatter being locked in translation in the manipulation handle. In asecond embodiment, the wire remains attached to the capsule after it hasbeen separated from the catheter, so as to act as a safety wire in caseit is necessary to reoperate on the capsule after implantation.

EP 2394695 A1 (Sorin CRM SAS) discloses another autonomous intracardiaccapsule assembly with an implantation accessory. The capsule holds onthe sidewall of the tubular body coupling fingers cooperating with ahelical guide carried by the distal end of the implantation accessory.The direction of helix of the helical guide is opposite to that of theanchoring screw of the capsule, so as to transmit the screwing torque ofthe anchoring screw in the heart wall. Then after the front face of thecapsule is coming to bear against this wall, the progressive separationof the capsule with the implantation accessory occurs by furtherscrewing of the catheter causing the coupling fingers to slide betweenthe turns of a helical compression spring. The torque limiter effect isthus being obtained by the compression of this helical spring.

The acceptance by practitioners of the technique of endocardial leadlesscapsules involves being able to offer a delivery system that is able tosecure the implementation of these capsules and may include thefollowing advantageous features:

-   -   Procedure similar to the current practice, which makes use of        well-known and mastered practitioners gestures: subclavian or        femoral puncture, insertion and manipulation of a catheter via        preformed stylets during the approach phase of the selected        implantation site, fastening of the screw or barb type, catheter        manipulation of the electrophysiology type, etc.;    -   Standard environment of the operating room;    -   Limiting the risk of coring of the tissues due to excessive        tightening which may damage the wall or worse, puncture it        (especially in the case of implantation into a thin wall as the        atrial septum or the apical region the right ventricle);    -   Possibility of intraoperatively or postoperatively removing        and/or repositioning in case of problems, even after release of        the capsule;    -   No risk of migration of the capsule during the acute phase        response;    -   Certainty of a good fixation of the capsule before removing the        implantation accessories, this constraint being the most        critical of all;    -   System natively designed for a femoral approach (see below);    -   For vessels and heart chambers, no risk of damage by the        anchoring member (screw, hook, needle, etc.) throughout the        implantation method, including the navigation in the venous        network and the approach phase to the selected implantation        site;    -   Quick procedure, with an implantation target time of        approximately 30 minutes ‘skin-to-skin’, comparable to that of        the implantation of a generator and a conventional ventricular        lead;    -   Safe operation, including in the case of: i) improper handling,        with in this case inability to jettison the capsule if screwing        of the anchoring member is incomplete, and/or ability to recover        the capsule during the procedure, and ii) premature        discontinuation of the procedure;    -   Low cost of manufacturing of the complete implantation system,        notably through the use of proven technologies and components in        similar applications.

A further difficulty arises with the current leadless capsules due totheir relatively large dimensions, with a typical diameter of about 4-7mm and a length of 15-40 mm. Indeed, to reach a heart chamber, and inparticular to reach the apex of the right ventricle, with an object ofthis size there is no routine procedure by high approach, that is to sayvia the subclavian vein. It is therefore necessary to use a differentapproach, from a femoral puncture then to go back in the inferior venacava to the heart.

Such a femoral approach is recognized as more difficult, especiallybecause of the large angle between the inferior vena cava and the axisof the right ventricle. Indeed, in the case of a high approach, at thearrival in the atrium, the distal portion of the implantation catheteris naturally oriented towards the apex of the right ventricle. At thispoint, one just has to push the catheter through the tricuspid valve andreach the bottom of the ventricle, wherein the anchoring member may bescrewed to the wall after landing. However, in the case of a femoralapproach, once the atrium is reached it is necessary to perform aturning maneuver of the distal end of the catheter to guide the lattertowards the ventricle and allow it to pass through the tricuspid valveand continue to progress in the right direction, towards the apex of theventricle.

For this purpose, well-known steerable catheters exist, the tip of whichis operated from the proximal handle so that it can perform such areorientation maneuver in the atrium under image intensifier. But afinal challenge remains in the final approach phase, as part of thesteerable catheter may be too short or poorly shaped to allow dockingwith the wall of the ventricular apex.

There is therefore the need to have an implantation accessory for fineadjustment and precise approach of the implantation site with largedifferences in myocardium anatomy.

SUMMARY

The invention discloses, in a first aspect, to use a steerable catheterand to extend it distally by a projecting cylindrical tip containing thecapsule to be implanted. This capsule is maintained in the retractedposition in the tip via a sub-catheter inserted into the inner lumen ofthe first catheter, the capsule and the sub-catheter being temporarilylinked by a single disconnectable mechanism fixed on the sub-catheterand allowing a complete screwing of the capsule in the tissue beforerelease. The telescopic configuration of the sub-catheter allowsprojecting the capsule out of the protection tip and beyond the latteron several centimeters, permitting in all cases a complete and accurateapproach of the capsule to the bottom of the ventricle.

According to a second, more general, aspect the invention discloses asimple switchable mechanism provided between a implantation accessoryand a medical device (corresponding, respectively, to the sub-catheterand to the leadless capsule in the previous particular case). Thismechanism consists of an elastic deformable component used in radialcompression, that is to say for its pinch effect and not for its axialtensile/compression effect. Such an elastic component may be a coilspring, and can play both the role of a releasable connection and oftorque limiter against excessive tightening action which could result ina coring of the tissues.

More specifically, according to the aforementioned first aspect, theinvention discloses a set of intracardiac capsules with its in situimplantation accessory, of the type disclosed by EP 2394695 A1aforementioned, that is to say including an autonomous capsule with acylindrical tubular body provided at its distal end by an anchoringmember adapted to penetrate a tissue wall of a cavity of the heart, andan implantation accessory of this capsule. The implantation accessoryincludes a catheter with an inner lumen, extended at its distal end by atubular protection tip defining an interior volume capable of housingthe capsule, and disconnectable mechanisms for supporting and guidingthe capsule to the implantation site.

Typically of the invention, the catheter is a remotely steerablecatheter. The implantation accessory further includes a sub-catheterhoused within the lumen of the remotely steerable catheter, and having adegree of freedom in translation and a degree of freedom in rotationrelative to the remotely steerable catheter. The sub-catheter and thecapsule are telescopically extendable with respect to the remotelysteerable catheter between i) a retracted position wherein the capsuleand its anchoring member are completely housed inside the tubularprotection tip, and ii) a position wherein the capsule is deployed outof the tubular protection tip and is carried by the distal end ofsub-catheter. Finally, the distal end of the sub-catheter and theproximal region of the capsule are provided with a first fasteningmechanism for mutually securing in translation and in rotation. Thefastening mechanism may be disconnectable under the effect of a rotationapplied to the sub-catheter from the proximal end thereof.

In a preferred embodiment, the implantation accessory further includes aretaining wire housed in a lumen of the sub-catheter that links thecapsule to the proximal end of the sub-catheter. The retaining wire ismovable within the lumen of the catheter so as to allow removal of thelatter, thereby leaving the capsule and the retaining wire in place. Theproximal region of the capsule and the distal end of the retaining wireare provided with a second disconnectable fastening mechanism forsecuring in translation and in mutual rotation.

The retention wire may be a particular wire adapted to transmitrotational torque from its proximal end to its distal end, and thesecond fastening mechanism includes a rotational connection separableunder the effect of said torque applied to the retaining wire, includinga threaded element formed at the distal end of the retaining wire andcooperating with a threaded part formed at the proximal end of thecapsule, or vice versa.

In a preferred embodiment, the first disconnectable fastening mechanismincludes a deformable elastic component, such as a helical spring whichcooperates with a rigid object, such as a central core on the capsule.The spring extends around the core such that it exerts on the latter aradial constriction effect, the spring and the core being configured tobe disengaged under the effect of a torque applied to the spring at oneend thereof, having the effect to reduce said radial constriction torelease the core.

Preferably, the proximal end of the spring is secured to the distal endof the sub-catheter. The distal end of the spring is preferably free.The core is preferably an axial lashing rod carried by the proximal endof the capsule and secured in rotation with the latter.

When the capsule includes an anchoring screw, the direction of the coilspring is the same as that of the anchoring screw. The value of thetorque applied to the spring that is effective to reduce said radialconstriction to release of the core is determined. This torque valuedepends on the geometry of the spring and of the elasticity of thematerial which constitutes it, so as to be always lower that apredetermined limit value that is corresponding to a limit holdingtorque of the anchoring screw in the tissue of the implantation site,without coring of this tissue.

Furthermore, to allow the introduction of the assembly, it is possibleto use a guidewire. In such embodiments, the protection tip thenincludes in the thickness of its peripheral wall a lateral lumenextending axially and opening at both the distal and proximal sides ofthe tip. This lumen being adapted to receive the guidewire and to allowthe sliding thereon of the implantation accessory with the capsulehoused in the protection tip. Finally, the protection tip preferably hasat least one vent hole, and at least one radiopaque marker.

According to the aforementioned second aspect, the invention disclosesan assembly of the type disclosed in EP 2394695 A1 cited above,particularly, including a medical device provided at its distal end withan anchoring member capable penetrating a tissue wall of a body, and anin situ implantation accessory of the medical device. The implantationaccessory according to the present invention includes a deformableelongate tubular member having a disconnectable mechanism for support ofthe medical device and guiding of the medical device to a site ofimplantation. The disconnectable mechanism includes a helical springcooperate with a central core and is suitable for securing intranslational and in mutual rotation the tubular element of theimplantation accessory and the medical device, and able to decouple themedical device with the tubular member of the implantation accessoryunder the effect of a rotation applied to the tubular member from theproximal end thereof.

Typically, the spring extends around the core with an adjustment suchthat it exerts on the latter a radial constriction effect, the springand the core being capable of disengagement under the effect of acombined torque and traction applied to the spring at one end thereof,being effective to reduce said radial constriction to release the core.

Preferably, the proximal end of the spring is secured to the distal endof the tubular member of the implantation accessory, the distal end ofthe spring is free, and the core is an axial lashing rod carried by aproximal end of the medical device and secured in rotation to thelatter.

When the medical device bears an anchoring screw, the direction of thecoil spring is the same as that of the anchoring screw. The value ofsaid torque applied to the spring that is effective to reduce saidradial constriction to release of the core is determined. The torquevalue depends on the geometry of the spring and the elasticity of thematerial which constitutes it, so as to be always lower to apredetermined limit value, corresponding to a holding torque limit ofthe anchoring screw in the tissue of the implantation site, withoutcoring of this tissue. Finally, the distal end of the spring isadvantageously a rounded end.

According to another aspect of the invention, an intracardiac assemblyincludes an autonomous capsule including a cylindrical tubular bodyprovided at its distal end with an anchoring member adapted to penetratetissue of a wall of a cavity of a heart and an implantation accessory.The implantation accessory includes a subcatheter configured to bereceived by, and move in rotation and in translation relative to, acatheter. The subcatheter includes a first fastening mechanism to couplethe distal end of the subcatheter to a proximal end of the autonomouscapsule. The first fastening mechanism comprises a torque limitationsystem configured to limit the torque transmission capacity from thesubcatheter to the autonomous capsules.

According to yet another aspect of the invention, a method forimplanting a medical device includes introducing a medical deviceprovided at its distal end with an anchoring member adapted to penetratetissue of a wall of a cavity of a heart to a target location in a cavityof the heart, wherein a proximal end of the medical device is coupled toa distal end of a subcatheter with a first fastening mechanism, whereinthe subcatheter and the medical device are introduced to the targetlocation through a catheter. The first fastening mechanism comprises atorque limitation system to control the torque provided to the anchoringmember. The method further includes rotating the subcatheter to engagethe anchoring member with the tissue of the cavity of the heart toimplant the anchoring member into the tissue. After implantation,rotation of the subcatheter continues in the same direction so as togenerate an excess torque at the torque limitation system to therebyrelease the first fastening means and decouple the subcatheter from themedical device.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates the implantation accessory of the invention and itscapsule, in position, with a schematic representation of the femoralapproach and of the chambers of the heart.

FIG. 2 shows the distal end of a remotely steerable catheter providedwith its protection tip, in the retracted position of the leadlesscapsule.

FIG. 3 is an enlarged, sectional view of FIG. 2, showing the generalconfiguration of the various internal elements and the leadless capsulehoused inside the protection tip.

FIG. 4 is an enlarged view of the sectional view of FIG. 3, in theregion of the connection with the proximal end of the leadless capsule.

FIG. 5 separately shows the radial compression coil spring mounted onthe end of the sub-catheter.

FIG. 6 is a sectional view corresponding to FIG. 5.

FIG. 7A is a sectional view showing a socket of a hollow cylinderhousing a lamella.

FIG. 7B is a sectional view corresponding to FIG. 7A.

FIG. 7C is a sectional view of a non-deformable axis inserted into thehollow cylinder housing of FIG. 7A.

FIG. 7D is a sectional view corresponding to FIG. 7C.

FIG. 8 shows the distal end of the remotely steerable catheter providedwith its protection tip mounted on a coiled guidewire used to advancethis tip from the femoral puncture until the selected implantation site.

FIG. 9 shows the distal end of the remotely steerable catheter providedwith its protection tip, with the leadless capsule partially emerged ofthis tip.

FIG. 10 is an enlarged, sectional view of FIG. 9, showing the generalconfiguration of the different internal elements.

FIG. 11 is an enlarged and sectional homologous view of FIG. 10, oncethe capsule is implanted in the chosen site, after removal of thesub-catheter and with the retaining wire still in place.

FIG. 12 shows the final configuration of the capsule and theimplantation accessory in the situation corresponding to that of FIG.11.

DETAILED DESCRIPTION

An exemplary embodiment of the device of the invention will now bedescribed. FIG. 1 illustrates a schematic representation of the femoralaccess route and the chambers of the heart, and depicting theimplantation accessory according to the present invention bearing anautonomous capsule of the leadless type 10.

Such a leadless capsule (shown in more detail in particular in FIG. 11)includes a tubular body 12 provided at one of its ends with a projectinghelical anchoring screw 14 axially extending from the tubular body andintegral with it in rotation. The anchoring screw 14 includes in itsdistal portion a length of the order of 1.5 to 2 mm of non-contiguousturns, adapted to penetrate the heart tissue so as to secure the capsulethere. The screw 14 can be an electrically active screw, comprising thedetection/stimulation electrode at least at its distal end, or it can bea passive screw serving only to the anchoring of tubular body 12 in thewall of the heart chamber. In the latter case, the capsule is providedwith an axial conductive needle 16 acting as a detection/stimulationelectrode in contact with the myocardial tissue. Alternatively, it isalso possible to provide a surface electrode.

The tubular body 12 includes various power supply circuits and methodsfor signal processing and wireless communication for the exchange ofsignals with a remote master device, implanted or not. These aspects arein themselves known, and since they are not part of the invention, theywill not be described.

At its proximal end 18, the tubular body 12 of the capsule 10 includesan axial lashing rod 20 with a rounded end, the function of which willbe described later in the implantation procedure. This lashing rod 20 issmooth on its outer face and has an internal threaded axial hole, astructure which will be explained in more detail with the description ofFIG. 4 below.

The leadless capsule 10 is intended to be implanted in the rightventricle 22, especially at the bottom of the ventricle, in the regionof the apex 24. For a conventional stimulation lead (connected to aremote generator), the location would typically be performed via thesubclavian vein 26, as illustrated in dashed lines at 28, so that theend of the lead would be approximately oriented in the ARV axis of theright ventricle and thus could easily pass through the tricuspid valveand reach the apex of the ventricle 24. However, as mentioned in theintroduction, this implantation approach is not feasible forimplantation of leadless capsules, the dimensions and, in particular,the external diameter, being far superior to those of the head of aconventional lead.

It is therefore necessary to access, via the vena cava 30, from afemoral puncture 32. But in this case, the axis of approach, that is tosay the AVC axis of the vena cava, has a strong angulation (angle 34)with the axis ARV of the right ventricle. Therefore, it is necessary toform a curvature 36 at the right atrium 38 in order to pass theimplantation accessory emerging from the sinus 40 of the vena cava tothe tricuspid valve 42 to then reach the cavity 22 of the rightventricle. Similar difficulties arise for implantation into the leftventricle, the implantation access then involving an arterial femoralpuncture and the passage of the aortic arch.

Such a maneuver can be performed through a “steerable” catheter, with acatheter tube 44 handled from the proximal end by an operating handle 46available to the practitioner. Using the handles 48, 48′ the latter cancreate and adjust a curvature 50 to guide the distal end 52 of catheter44 accurately, typically with an orientation up to 180° in bothdirections with a variable radius of curvature, of the order of 5 to 60cm. The handle 46 is also provided with a purge drain lateral track 54and of a valve 56, features which are in themselves entirelyconventional.

With a conventional steerable catheter, if it is possible to preciselyadjust the curvature 50, it is not possible to change the area of thecatheter wherein, along its length, the curvature is formed. However, inthe particular case illustrated with a femoral approach, with theobjective of reaching the bottom of the right ventricle, this limitationcan be troublesome with some specific morphologies with very elongatedcavity. Indeed, the distal portion 52 of the steerable catheter locatedbeyond the curvature of the region 50 may be too short to reach theregion of the apex 24. Embodiments of the present invention address thisdifficulty, as will be explained hereinafter, so that the implementationof the invention is possible using a marketed, pre-existing, steerableconventional catheter to reduce the cost of the implantation accessoryof the invention.

FIGS. 2 to 4 show, in enlarged views, the distal end of the steerablecatheter 44, with the different characteristic elements of theinvention. The steerable catheter 44 is provided at its distal end witha tubular protection tip 58 having a central recess 60 (FIG. 3) forhousing the capsule 10 in a configuration called “retracted position”,corresponding to FIGS. 2-4. The main function of the tip 58 is toprotect the capsule, including the anchoring screw 14, during theintravenous passage of curves, angulations, valves, etc. Conversely, thecap protects the tissue from the risk of stripping potentially caused bythe movement of translation of the screw.

The outer diameter of the steerable catheter 44 is typically between 10and 15 French (6.6 to 10 mm), for an inner lumen diameter of between 8and 12 French (2.66 mm to 4 mm). The tubular tip 58 must be able tohouse the capsule and therefore have an inside diameter of about 21French (7 mm). Furthermore, a catheter of this size must necessarilymove into the venous system while being guided by a coiled guidewirepreviously introduced into the vasculature.

As in the illustrated design, the central canal of the catheter 44 isblocked by the capsule. To allow the introduction of a guidewire, thetubular tip is provided with an eccentric lateral lumen 62 extendingaxially the length of the tip and opening at the distal 64 and proximal66 sides, preferably extending over the entire length of the tip 58. Theinner diameter of the lateral lumen 62 allows for the introduction of aconventional coiled guidewire of a diameter of 3 French (1 mm), and thesliding of the tip, and therefore of the entire steerable catheter 44,through the vasculature (this configuration is notably shown in FIG. 8,wherein the reference 98 designates the coiled guidewire).Alternatively, the eccentric lateral lumen 62 may be extended along thebody of the steerable catheter 44 to facilitate the pushing of thecoiled guidewire and prevent any curling phenomenon thereof.

Note that the eccentricity of the lumen 62 combined to the beveledprofile of the tip allows easy progression into the venous system by a“sidewire” technique. In addition, the front panel 68, the most distalarea of the tip 58, is shaped to have a minimum front bearing surface toavoid any risk of perforation in case of accidental operation withoutthe coiled guide.

In addition, a radiopaque marker 70 is provided in front of the tubulartip 58 on the most distal surface of this tip, to more efficientlyidentify the capsule outlet if the tip is made of a radio-transparentmaterial. Finally, one or more drain holes 72 are disposed proximal tothe tip, to prevent piston effect upon injection of contrast medium,which otherwise would result in pushing the capsule 10 out of theprotection tip 58.

The catheter 44 is formed with a reinforced structure, such as a wiremesh or a coil embedded in the thickness of the catheter wall, so as toprovide a torque transmission capability exerted on the proximal handleto the distal end (reinforced structure 74).

The implantation accessory of the invention further includes, typically,a sub-catheter 76, introduced into the central lumen of the steerablecatheter 44, and movable in rotation and in translation relative to thelatter. The function of this sub-catheter 76 is to ensure the deploymentof the capsule out of the protection tip and to advance the capsule tothe implant site by a translation movement over a sufficient length,typically from to 2 to 6 cm depending on the anatomy of the patient. Inthe figure, arrow 78 indicates the translation of the sub-catheter 76within the steerable catheter 44, and arrow 80 indicates the translationof the capsule 10 out of the protection tip 58. The sub-catheter 76 alsohas the function of ensuring the transmission of torque from theproximal end (at the operating handle) to its distal end, and isprovided for this purpose of a reinforced structure 82.

It is possible to use as the sub-catheter 76 a conventional guidecatheter sized from 4 to 6 French (1.33 to 2 mm), which is an existing,simple and cost-saving device meeting the current constraints torquetransmission, low coefficient of friction inside and outside,flexibility, etc. Sub-catheter 76 may have a proximal “Luer-Lok”connection for the rapid mounting of a multifunction adapter such as arotational hemostasis valve or other adapter compatible with this sealedconnection standard. Alternatively, the sub-catheter 76 can be used toinject a contrast to the back of the capsule 10 so as to accuratelymonitor the operation under fluoroscopy.

A fastening mechanism according to the present invention is directed tothe coupling of an implantation device including a hollow or notelongated tubular member (such as a catheter) with an autonomous (suchas a leadless capsule) or not (such a probe head of a pacing lead)medical device, said device being provided at its distal end with ananchoring mechanism adapted to penetrate a cardiac or else body tissue.The fastening mechanism according to the invention employs an elasticdeformable component, such as helical spring 84, which is not used forits properties of elasticity in axial traction/compression (effectresulting from the elongation or the reconciliation of the coils of thespring), but for its radial compression properties, that is to say forthe pinch or throttle effect can such a spring can exert around a rigidcomponent, such as a core inserted into the helical form. In otherembodiments, the elastic deformable component may be a lamella thatprovides radial compression about the core.

The geometry of the elastic deformable component, such as a spring, andthe elasticity of the material which constitutes it are chosen so as toproduce between the elastic component and the core, in the absence ofexternal stress, an interference fit (caused by the radial compressionresulting from the pinch effect). In the illustrated example of FIG. 4of the leadless capsule 10, the core is constituted by the lashing rod20 with rounded end, located axially on the proximal portion 18 of thecapsule 10 and outwardly oriented. This lashing rod 20 may be shaped tooptimize the disengagement function.

The spring 84 is shown in detail and in isolation in FIGS. 5 and 6. Thespring 84 is secured to the distal end of the sub-catheter 76 by turns86. This securing in translation and in rotation, for example by weldingor gluing, must be kept regardless of the degree of stress normallyapplied to the sub-catheter 76 and to the spring 84.

The turns 88 located distally of the spring 84 are free turns, which aresurrounding the lashing rod 20 but which are not mechanically fastenedto the latter by connection mechanisms other than interference fit withtightening obtained in the static configuration of these two elements.In addition, the distal end of the spring 84 is preferably a rounded endto prevent tissue injury and hang at various manipulations. The inactiveturns 86 and/or the active turns 88 may be either touching or notcontiguous.

Once the capsule 10 is fixed to the implant after complete penetrationof the anchoring screw 14 to the front face of the capsule, thepractitioner continues to make the sub-catheter 76 turn, therebygenerating an excess torque. The excess torque has the effect ofreducing the force exerted by the free turns 88 on the lashing rod 20,to cause rotational sliding of these turns on this same rod. Bycombining this rotational movement to a slight tensile load, thecompression spring 84 is released from the lashing rod 20, bylongitudinal sliding of the turns on the rod, thus releasing the capsule10 from the spring 84, and thus from the sub-catheter 76.

In an alternative embodiment of the first fastening mechanism, shown inFIGS. 7A-7D, the deformable plastic member is a lamella 184 that ispositioned in a socket created by a hollow cylinder 186. The lamella 184is radially deformable relative to the cylinder axis. The rigidcomponent is provided in the form of a non-deformable axis 188configured to be introduced into the socket of the hollow cylinder 186.The introduction causes deformation of the lamella 184, therebyproducing a radial force between the non-deformable axis 188 and thelamella 184, as shown in 7D. Relative rotational movement between thehollow cylinder 186 and the non-deformable axis 188 generates atangential calibrated friction and therefore creates a limitation in thetorque applied to the components of the system.

The radial compression spring 84 or lamella 184 thus act as torquelimiter. Indeed, with the anchoring screw of a standard leadlesscapsule, if the practitioner continued rotation of the sub-catheter 76and therefore of the capsule 10, the torque would increase and exceed alimit C_(coring). This increases the risk of the anchoring screw locallytearing the tissues under the effect of the rotation of the screwadvance thereof, causing a tearing of the tissues and, in the extreme, aperforation of the wall, with the risk of tamponade. This is not thecase with the device and methods provided by the invention. Thepractitioner may indeed safely continue rotating the sub-catheter 76,always in the same direction (usually clockwise), because the extratorque due to the reaction of the anchoring screw anchored in the tissueis absorbed by the connection between, for example, the spring 84 andthe lashing rod 20 (phenomenon of sudden increase of the torque when thefront face of the capsule contacts the cardiac tissue). Morespecifically, the geometry and elasticity of the spring 84 are chosen soas to define a predefined torque C_(release) lower to the coring limit,C_(coring), corresponding to a limit holding torque of the anchoringscrew in this tissue, without coring of the tissue, while providing afull screw (tissue contacting the front face of the capsule). Thus, whenthe C_(release) torque is reached, the further rotation of thesub-catheter 76 in the clockwise direction causes, in combination with aslight traction force, the gradual release of the spring 84 with thelashing rod 20 by longitudinal sliding of the turns of the radial springalong the rod. In case of any excess torque, the turns of the radialspring slide in rotation on the securement ring therefore no longertransmit torque elevation. The clutch release torque C_(release) isadjusted to a typical value of about 0.01 to 0.05 N·cm.

Furthermore, in a static configuration, the pinch force of the freeportion 88 of the spring 84 on the lashing rod 20 is selected so as toprevent accidental disassembly by a traction force (axially directedforce) lower to a sufficient threshold, typically a threshold whichprovides holding even for a traction exerted on the sub-catheter 76under a force of up to 20 N.

Note also that if it is desirable to unscrew the capsule, for examplebecause after a first implantation it is found that the electricalperformance of the site are not satisfactory, the coupling system by thespring 84 will have no release effect during unscrewing. Since thespring will then be driven in reverse rotation (usuallycounterclockwise), this will further increase the effect of thetightening of the turns 88 of the lashing rod 20.

Another advantage of the spring 84 is after the release of the capsule,the implantation device is present with a screw at its end in the formillustrated in FIGS. 5 and 6. In particular, the free turns 88 of thespring 84 form a screw. In case of reoperation intraoperative, that isto say, if it is desirable to secure the new sub-catheter 76 to thecapsule, the screw formed by the spring 84 will have the advantage ofrequiring no angular adjustment to secure the lashing rod 20 of thecapsule to be retrieved (unlike the systems using a male/femaleconnector which require positioning to allow the interlocking of the twoelements).

Finally, note that the torque limiter comprising spring 84 isconveniently located in the chain of transmission of forces.Specifically, any loss of fidelity in the transmission of torque betweenthe proximal end of the sub-catheter 76 (that is to say from the handlemanipulated by the practitioner) and its distal end (the location of thecoupling spring 84) has no effect on the maximum or minimum torque atthe interface between the anchoring screw and the tissue, which is aguarantee of complete fixation. This is not the case for a detachablesystem that would be located further upstream, typically in theoperating handle 46. Note also that all of these features are obtainedvia a very economical component of very simple and compact design.

The release of the capsule may thus be effected by a combined screwingand traction movement in two steps. First, screwing of the capsule inthe heart wall, by clockwise rotation of the sub-catheter 76 (e.g. 10rpm) under a slight push. Second, release of the capsule by a furtherclockwise rotation of the sub-catheter 76 (e.g. 5 turns) under slighttension to allow removal of the sub-catheter after release of the spring84. To obtain this result, the direction of the turns of the spring isof course selected in the same direction as that of the anchoring screw,preferably with a right-engaging thread, so that the screwing of thecapsule and then its release correspond to a rotation of thesub-catheter 76 in the clockwise direction, the most conventional one.

Advantageously, the implantation kit also includes a security thread orretainer 90 of “breadcrumb” wire-type connected to the capsule 10 on thedistal side, extending over the entire length of the sub-catheter 76 andexceeding it proximally, that is to say on the side of the operatinghandle 46.

As shown in FIGS. 11 and 12, once the capsule 10 is implanted anddropped, its operation is tested, including the establishment of goodwireless communication between the capsule and the remote master deviceas well as the stimulation electrical performance.

Once the steerable catheter 44 and the sub-catheter 76 are completelyremoved, the retaining wire allows for intraoperatively retrieving thecapsule, with reintroduction of the implantation accessory by making itslide along the retaining wire until the protection tip 58 caps thecapsule. The latter can then be re-coupled to the sub-catheter by aclockwise rotation (the clutch-limiter functionality being alwayseffective). The capsule can then be unscrewed from the wall 100 by acounterclockwise rotation and repositioned at another site by the sameprinciple as what has been described above, by a clockwise rotation ofthe sub-catheter.

The retaining wire is for example a wire of 1 French diameter (0.43 mm)having at its distal end 92 a thread 94 able to cooperate with a matinginternal thread 96 formed in a threaded axial bore of the stowage axis20 (FIG. 4). This retaining wire is preferably sufficiently flexible inits distal part (6 to 8 cm), while being able to transmit to the distalend 92 an unscrewing torque resulting from a rotation exerted from theproximal end, at the operating handle. Note that, because of the verysmall diameter of the screwing system 94, 96, the torque to be exertedto produce the unscrewing is very small (of the order of 0.02 N·cm), andmay not in any way exert trigger a rotation movement of the capsule 10which is firmly secured to the heart wall by the anchoring screw. Theretention wire may be colored in different colors for each of theimplanted capsules, so as to more easily identify the appropriatecapsule in the event of reoperation.

The technique of the invention therefore provides triple securitythrough the release system which allows at the release of the capsule:

-   -   To ensure complete screwing of the capsule in the tissue;    -   To prevent coring of the heart wall; and    -   To ensure the practitioner to recover the capsule after dropping        in case of difficulty, through the retaining wire.

The procedure for setting up the leadless capsule through theimplantation accessory as described above comprises the following steps,each of which is relatively conventional and can be easily performed bya practitioner without requiring special skills or additional maneuvers:

-   -   Right or left femoral puncture, in order to access the inferior        vena cava 30;    -   Optional percutaneous introduction of a 23 French haemostatic        introducer (7.66 mm);    -   Insertion of the steerable catheter 44 on a spiral guidewire        (illustrated at 98 in FIG. 8), typically a 3 French (1 mm)        guidewire on which the tubular tip 58, and thus the steerable        catheter 44 will slide and move to the right atrium 38;    -   Turning maneuver of the tip of the steerable catheter 44 (as        shown at 36 in FIG. 1) and introduction of the tip 58 in the        right ventricle;    -   Release of the capsule 10 to the apex of the ventricle by        translation of the sub-catheter 76 in the steerable catheter 44        (configuration shown in FIG. 10);    -   Visualization of the cardiac walls by injection of contrast        medium through the sub-catheter;    -   Fine positioning of the capsule to the selected target site,        with the possibility of translation once in the cardiac cavity        by a more or less important deployment of the sub-catheter 76        from the steerable catheter 44, allowing fine adjustment to suit        a wide variety of anatomies;    -   Screwing of the capsule in the heart wall to the release of the        radial compression spring 84;    -   Separation of the sub-catheter 76 with the capsule 10, and        removing of the sub-catheter 76 out of the steerable catheter 44        (configuration shown in FIG. 11);    -   Electrical test of the capsule;    -   Complete removal of steerable catheter 44 and of the        sub-catheter 76;    -   Final release of the capsule, with withdrawal of the retaining        wire 90 by low torque unscrewing; and    -   Closure of the puncture site.

1. A stimulation system comprising: a capsule comprising a central core;a subcatheter; and a fastening mechanism configured to couple thesubcatheter and the capsule in translation and in mutual rotation, thefastening mechanism comprising: a helical spring comprising active turnsand inactive turns, wherein the inactive turns are fixedly coupled tothe subcatheter; wherein the active turns are structured to extendaround the core such that the helical spring exerts a radialconstriction on the core; and wherein the helical spring is structuredto disengage from the core under an effect of a combined torque andtraction applied to the helical spring effective to reduce the radialconstriction until the release of the core.
 2. The stimulation system ofclaim 1, wherein the helical spring is an elastic deformable componentand the core is a rigid component, wherein the helical spring and thecore are configured to slide relative to one another in a slidemovement.
 3. The stimulation system of claim 2, wherein the slidemovement between the helical spring and the core is a longitudinal slidemovement.
 4. The stimulation system of claim 1, wherein a force of theradial compression creates an interference fit between the helicalspring and the core.
 5. The stimulation system of claim 1, wherein thefastening mechanism is coupled to a distal end of the subcatheter. 6.The stimulation system of claim 1, wherein the core is an axial lashingrod.
 7. The stimulation system of claim 1, wherein the distal end of thehelical spring is free.
 8. The stimulation system of claim 1, whereinthe helical spring limits the torque transferred from the helical springto the capsule under a predetermined torque value.
 9. The stimulationsystem of claim 8, wherein the predetermined torque value is determinedbased on the elasticity of a material of the helical spring.
 10. Thestimulation system of claim 1, wherein the torque and traction areapplied to a distal portion of the helical spring.
 11. A subcatheterhoused within a steerable catheter comprising: a fastening mechanismstructured to couple to the subcatheter, wherein the fastening mechanismis structured to couple the subcatheter to a capsule in translation andin mutual rotation, the fastening mechanism comprising: a helical springcomprising active turns and inactive turns, wherein the inactive turnsare fixedly coupled to the subcatheter; wherein the active turns arestructured to extend around the core such that the helical spring exertsa radial constriction on the core; and wherein the helical spring isstructured to disengage from the core under an effect of a combinedtorque and traction applied to the helical spring effective to reducethe radial constriction until the release of the core.
 12. Thesubcatheter of claim 11, wherein the spring is an elastic deformablecomponent and the core is a rigid component, wherein the helical springand the core are configured to slide relative to one another in a slidemovement.
 13. The subcatheter of claim 12, wherein the slide movementbetween the helical spring and the core is a longitudinal slidemovement.
 14. The subcatheter of claim 11, wherein a force of the radialcompression creates an interference fit between the helical spring andthe core.
 15. The subcatheter of claim 11, wherein the fasteningmechanism is coupled to a distal end of the subcatheter.
 16. Thesubcatheter of claim 11, wherein the core is an axial lashing rod. 17.The subcatheter of claim 11, wherein the distal end of the helicalspring is free.
 18. The subcatheter of claim 11, wherein the helicalspring limits the torque transferred from the helical spring to thecapsule under a predetermined torque value.
 19. The subcatheter of claim18, wherein the predetermined torque value is determined based on theelasticity of a material of the helical spring.
 20. The subcatheter ofclaim 11, wherein the torque and traction are applied to a distalportion of the helical spring.